Add missing tutorial models

[javagl]

Fixes #70

Some models that are shown in the glTF tutorial had been missing here. From the ones that are listed in the issue, SimpleSkin was already added a while ago. The SimpleTexture and SimpleMeshes samples are added here.

I also cleaned up some of the README.body.md files of the other tutorial models, and added links to the respective sections of the tutorial.

(I think the LICENSE.md files will be created/overwritten during the model index update - but it's all CC0, so there shouldn't be any changes anyhow...)

[emackey]

I think this name field should have a space. "Simple Material"

[emackey]

Actually this repo is very inconsistent about spaces in proper model names. But it has some, for example:

glTF-Sample-Assets/Models/BoxTexturedNonPowerOfTwo/metadata.json

Line 33 in 497c9c9

"name": "Box Textured not 2^N",

[emackey]

likewise

[javagl]

@emackey It's actually not soooo inconsistent: Nearly every name is just the ModelName with spaces to yield Model Name.

I just did that change for the newly added and previously existing "simple" (tutorial) models.

A few short notes that might be related (also @DRx3D ):

• For some reasons, I thought that name was supposed to be the name (as in "the directory- and file name"). So the purpose of the name should probably be added at https://github.com/KhronosGroup/glTF-Sample-Assets/blob/main/SubmittingModels.md#example-metadata-file . Maybe roughly something like

  "A short, human-readable name of the model. This will become the link text in the overview page, and the title of the README of the model"

  or so

• The Box With Spaces model currently is not displayed properly in the lists:
  
  Probably because ... it has spaces 😶

• I'd suggest renaming the glTFPotOfCoals model to PotOfCoals. We don't use "Smurf Naming" prefixes

(I'll note these as internal TODOs, but if desired, they can be escalated into issues, to prevent them sinking to the bottom of my TODO list...)

[emackey]

I'd suggest renaming the glTFPotOfCoals model to PotOfCoals. We don't use "Smurf Naming" prefixes

Agreed. Also PotOfCoals has a glTF-Animation folder, which none of the other animated models have. Are there GLBs with and without the animation? Why? This needs some cleanup too.